1. Field of the Invention
The present invention relates to a system and a method for supporting communications among plural ATM devices.
2. Description of the Prior Art
FIG. 23 shows a conventional method for connecting ATM devices 5. A device such as an ATM terminal or an ATM exchange having an ATM (Asynchronous Transfer Mode) interface (hereinafter referred to as an “ATM device 5”) performs communication with other ATM devices 5 via an ATM network as shown in FIG. 23. The ATM network enables a fast communication of multimedia data or the like. Therefore, a service for connecting ATM devices 5 to each other via the ATM network so as to establish a WAN (Wide Area Network) or the like is widespread.
However, a cost necessary for constructing and managing the ATM network is high, so a method for establishing a WAN at a lower cost is desired strongly.
On the other hand, as a method for establishing and operating a WAN, a method of connecting devices using a wide area Ethernet network has gained the spotlight. According to this method, a WAN can be established at a low cost.
Therefore, a method of replacing the existing ATM network for connecting ATM devices 5 with a wide area Ethernet network is possible. However, in such a method, it is difficult to predict a delay or a degree of dumping of frames in the wide area Ethernet network. Therefore, it is difficult to synchronize a clock of a lower order ATM device 5 with a clock of a higher order ATM device 5 of communication in the wide area Ethernet network. Accordingly, communication between ATM devices 5 cannot be performed well in the above-mentioned method.
As described in Japanese unexamined patent publication No. 7-264207, there is proposed a method of connecting a terminal device that is used in an Ethernet LAN (Local Area Network) environment to an ATM exchange simply. However, there is not proposed a method in which a wide area Ethernet network is used instead of the ATM network for communication between ATM devices 5.